1. Field of the Invention
This invention relates to a composition suitable for eliminating a thermosetting resin, and a thermosetting resin eliminating apparatus using the same.
2. Description of the Related Art
Generally, an active matrix liquid crystal display (LCD) uses a thin film transistor (TFT) as a switching device to display a moving picture. Since the LCD is able to provide a product having a smaller dimension than a Cathode Ray tube, it has been widely used in various applications including personal computer, notebook computer, office automation equipment such as a copy machine, etc., and portable equipment such as a PDA and a pager, etc.
Such an LCD typically uses a thermosetting resin such as polyimide, polyacrylate or benzocyclobutane, etc. as a material of a dielectric layer, an organic protective layer, an insulating layer, an alignment film, a black matrix and a color filter. However, this film or layer formation using said thermosetting resin raises a problem of a difficult stripping process. Thus, if a problem occurs with a film or layer made from a thermosetting resin in a process of manufacturing an LCD or a semiconductor, then the film or layer has been often discarded because of a difficulty of rework or reproduction. In order to prevent such a loss, a rework process for each process has been developed.
FIG. 1 and FIG. 2 shows a method of forming color filters step by step. Referring to FIG. 2, at step S1, Cr/CrOx or Cr/CrNx/CrOx is entirely deposited on a bare glass substrate 2 and thereafter patterned. Then, black matrices 4 are formed on the bare glass substrate 2 at step S2. Alternatively, the black matrices 4 made from a resin may be formed by entirely coating polyacrylate added with a black pigment on the bare glass substrate 2 and thereafter patterning it.
As a result of testing the black matrices 4 formed in this manner, if it is judged that a problem exists with the black matrices 4, a process of reworking the black matrices 4 is carried out at step S3. Herein, since the black matrices 4 are made from a thermosetting resin and because it is impossible to completely eliminate a thermosetting resin, black matrices made from a metal only is introduced into the rework process. After the black matrices 4 are formed, red, green and blue color filters 16R, 16G and 16B are sequentially formed on the substrate 2 at steps S4 to S6.
First, as shown in FIG. 1, a red resin 6 is entirely coated on the substrate 2 and then a photo mask pattern 8 is formed thereon. Next, the red resin 6 made from polyacrylate is patterned by an exposure and development process. Subsequently, the green filter 16G and the blue filter 16B are formed in the same manner. Since the color filters are made from a thermosetting resin that cannot be eliminated completely, a rework process is almost impossible. Finally, after the color filters 16R, 16G and 16B were formed, indium tin oxide (ITO) used as a common electrode is entirely deposited thereon (step S7).
In order to eliminate a thermosetting resin, a dry etching method is generally used. For instance, the substrate on which a thermosetting resin is formed into a film is mounted in a chamber to inject O2, O2+Cl2, CF4 or SF6, etc. into the chamber, thereby generating a plasma discharge. Then, a reaction between said injection gas and said thermosetting resin film occurs to entirely etch the thermosetting resin film. However, said dry etching method has various problems including imperfection in a post process such as a pattern badness and an electrical short badness, etc. Such problems are caused by an alien substance left at the surface after the thermosetting resin film was eliminated. For example, an under layer of the thermosetting resin film is damaged upon over-etching.
An alternative scheme for eliminating a thermosetting resin is a method of solving a problem of said dry etching and an ashing using an O2 plasma and taking advantage of a stripper of a stripping liquid so as to obtain a dry cleaning effect. However, since the known strippers can eliminate only a thermosetting resin of a specific material, for example, an alignment film (i.e., polyimide, etc.) of an LCD, its use has been limited. Some example stripper compositions are listed in Table 1 and Table 2.
Strippers for eliminating color filters having a composition indicated by the following Tables 1 and 2 are capable of eliminating a blue resin or blue and green resins, but are incapable of eliminating a red resin. As a practical matter, it is difficult for such strippers to eliminate a blue resin. This is caused by a fact that, since coating and patterning of a resin followed by a high-temperature curing process are repeatedly carried out in a sequence of a red resin, a green resin and a blue resin are repeated in the color filter formation process, a green resin and a red resin are over-cured in comparison to a blue resin.
TABLE 1Composition of stripper AMono Ethanol Amine 1.97%Methyl CARBITOL 6.97%Benzyl Alcohol10.87%NMP11.28%Diethyl CARBITOL11.19%1,3-Dimethyl-2-imidazolidone12.32%Water45.4%
TABLE 2Composition of stripper BMethanol 2.07%Mono Ethanol Amine 6.54%2-Ethylhexanol32.09%Water59.3%